My thought was that since I'm going to be a doctor one day then there is probably no reasonable income that would be beneficial to have a traditional IRA right? During residency, I will be around 50k/year,...
All depends on your marginal rate when contributing vs. your marginal rate when withdrawing.
Marginal rate is not necessarily the same as tax bracket, due to various credits, phase-outs, etc.
and after residency my salary will most likely surpass the deduction limit for a traditional IRA which makes a backdoor Roth more beneficial.
Or direct Roth, if your MAGI is above the deductible limit but below the direct Roth contribution limit.
Second, it seems to always make sense to contribute to a 401k or 403b because from what I can tell that amount is deductible at a high income limit. Is there even a limit?
Yes, this makes sense. There are some nuances about limits involving "highly compensated employees" but that's a topic for later discussion. ;)